The hypothesis underlying the study is that patients with cystic fibrosis associated liver disease (CFLD) will have low plasma concentrations of transforming growth factor beta (TGF-B), compared to patients with cystic fibrosis without evidence for liver disease. The study proposes to determine plasma concentration of TGF-B in a cross-section of patients with CFLD and age, sex, and pulmonary function matched controls with CF and no evidence of liver disease.